The semiconductor industry has progressed into nanometer technology process nodes in pursuit of higher device density, higher performance, and lower costs. As this progression takes place, challenges from both fabrication and design issues have resulted in the development of three-dimensional designs, such as fin-like field effect transistor (FinFET) device. A typical FinFET device is fabricated with a thin “fin” (or fin-like structure) extending from a substrate. The fin usually includes silicon and forms the body of the transistor device. The channel of the transistor is formed in this vertical fin. A gate is provided over (e.g., wrapping around) the fin. This type of gate allows greater control of the channel. Other advantages of FinFET devices include reduced short channel effect and higher current flow.
FinFET devices are compatible with a high-k metal gate (HKMG) process flow. In other words, FinFET devices may be implemented as HKMG devices that have a high-k gate dielectric and a metal gate electrode. However, existing HKMG FinFET devices still have shortcomings, for example shortcomings related to lack of threshold voltage (Vt) tuning options, which limits the IC circuit design freedom and could also degrade device performance.
Therefore, although existing HKMG FinFET devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect.